Development of novel peptides for blocking aggregation and caspase-3 cleavage of TDP-43

TAR DNA-binding protein 43 (TDP-43) is a protein that is thought to be involved the pathology of amyotrophic lateral sclerosis (ALS) and frototemporal lobar degeneration (FTLD). Several TDP-43 mutations have been found in sporadic and familial ALS and FTLD. In patients with these neurodegenerative diseases, TDP-43 forms insoluble inclusions in the nucleus and cytoplasm of neurons. Evidence shows that TDP-43 is abnormally cleaved by caspase-3 and that the truncated inclusions were toxic to cells, which may be the cause of neurodegenerative diseases. To explore novel treatments of neurodegenerative diseases, we identified regions in TDP-43 that are bound by TDP-43 itself or by caspase-3 using high density peptide array analysis. Based on the identification of the key regions, peptides that might be able to block the interactions were designed. We found our synthetic peptides could effectively inhibit the formation of TDP-43 protein aggregations in a concentration-dependent manner in Hela cells in which a mutated human TDP-43 gene was overexpressed. However, these peptides could not prevent cell death. These results suggest that TDP-43 aggregation is a consequence of the cell death process rather than a cause. In addition, the synthetic peptides that are able to block the binding of caspase-3 to TDP-43 in a cell-free assay were also effective in inhibiting the cleavage of TDP-43 in cultured neuronal cells after NMDA insults. Furthermore, application of our peptide was able to block NMDA-induced, caspase-3 dependent cell death. These results suggest new approaches to treatment of ALS and FTLD.Medicine, Faculty ofGraduat